Investigation Into Abnormal Surface Subsidence Above a Longwall Panel in the Southern Coalfield, Australia

摘要

The subsidence over a longwall panel at Tahmoor Mine inthe Southern Coalfield of NSW, Australia, was found to beapproximately twice the size it had been in previous measurements.An investigation into the potential causes was conducted usingcomputer modeling together with hydrological characterization anddetailed geotechnical characterization of the strata.The abnormal subsidence was found to be consistent withlocalized weathering of joint and bedding planes above a depressedwater table adjacent to an incised gorge. The study showed thatother factors such as variation in stress field, joint zones, variationin rock strength and topographic factors did have sufficient impactto induce the abnormal subsidence.The results have significant implications to subsidenceprediction in areas that may be prone to the phenomenon found atTahmoor. Key indicators of the potential for this form of abnormalsubsidence are presented.